P. 256. Turning Governor Balls.—The method already
described is adopted only where the special appliance shewn in
Fig. 740 is not readily obtainable. The slide D, with its tool
holder, is known as a ball-rest. It is pivoted at c, directly under
the centre of the ball to be turned, and is supported upon the
saddle B. The tool being set to turn the ball of correct diameter,
the necessary radial feed is given by hand. The feed is more
regular if spur teeth be cast upon the curve E, into which a pinion
on the rest engages. A horizontal hand wheel fits then on the
P. 256. Cutting Bevel-wheel Teeth.—If not too small
these wheels may be correctly cut by the machine in Fig. 741.
The bars r> D, carrying sliding toolboxes c c, are centred at A on a
universal joint, and as the tools reciprocate a slow conical feed is
obtained by guiding the bars round the plate on ' form ' E, which
is cut to twice the tooth scale and set at twice the distance from A.
(Seepp. 821 ^986.)